Merkley said the 39-page plan indicates the Department of Homeland Security requested $9.8 million from FEMA accounts. The documents said the money, about nine-tenths of one percent of FEMA's annual budget, would be transferred from FEMA's "Preparedness and Protection" and "Response and Recovery" undertakings to pay for detention beds and ICE's Transportation and Removal Program.

USA Today reported the story Wednesday, citing the same documents.

With Hurricane Florence bearing down on the East Coast, such a plan to funnel money away from FEMA has drawn substantial criticism. The Category 4 storm is expected to make landfall in North Carolina Thursday and may be the costliest hurricane in U.S. history.

Merkley said of the diversion of funds "is just incredibly irresponsible."

The plan indicates that millions of dollars earmarked for the Transportation Security Administration and U.S. Coast Guard have also been redirected to ICE.

Addressing the issue, DHS spokesman Tyler Houston said no funds were taken from disaster relief programs.

"This is a sorry attempt to push a false agenda at a time when the administration is focused on assisting millions on the East Coast facing a catastrophic disaster," Houston said. "The money in question, transferred to ICE from FEMA's routine operating expenses, could not have been used for hurricane response due to appropriation limitations."

It is not uncommon for cabinet-level agencies to swap money, but FEMA's budget was thrown into disarray by the number of hurricanes, fires and other natural disasters in 2017.

Earlier this year, thousands of families were separated and housed in detention centers as part of the administration's tougher immigration stance -- incidents that Merkely said may have increased ICE's need for more money.